The nonapeptide bradykinin is released by glandular or plasma kallikreins by their action on substrates in plasma called kininogens. Kininogens of high molecular weight (HMW-) and low molecular weight (LMW-) have been recognized in the plasma of man and other species. HMW-kininogen has recently been shown to participate in the intrinsic coagulation pathway, the contact activated fibrinolytic pathway as well as the kinin-forming system. In order to study the molecular basis for the action of HMW-kininogen in coagulation, fibrinolysis and related phenomena, we propose to prepare human HMW-kininogen in highly purified form. When this is achieved, we will characterize the molecule by its physical and chemical properties. We will then study the cleavage of human HMW-kininogen by human plasma kallikrein. The fragmentation products of human HMW-kininogen will then be assayed for their ability to reconstitute impaired coagulation or fibrinolysis of human HMW-kininogen deficient plasma by standard assays. It is not yet clear whether HMW-kininogen functions as a co-factor, like coagulation factors V or VIII, or whether it has enzymatic activity. In recent studies of fragmentation products of bovine kininogens, we have shown that a glycopeptide fragment of bovine HMW-kininogen is a permeability increasing agent which acts synergistically with bradykinin. We will ascertain whether such a glycopeptide fragment exists in human HMW-kininogen and study its function as well. If the human glycopeptide analog can be isolated and analyzed, the mechanism of its potentiation of bradykinin will then be studied. BIBLIOGRAPHIC REFERENCES: Matheson, R. T., Miller, D. R., Lacombe, M. J., Han, Y. N., Iwanaga, S., Kato, H. and Wuepper, K. D. Flaujeac Factor Deficiency: Reconstitution with Highly Purified Bovine High Molecular Weight-Kininogen and Delineation of a New Permeability-Enhancing Peptide Released by Plasma Kallikrein from Bovine High Molecular Weight-Kininogen. J. Clin. Invest. 58:1395-1406, 1976. Matheson, R. T., Kato, H. and Wuepper, K. D. Further Characterization and Inactivation of the Permeability-Enhancing Fragment (Peptide 1-2) of Bovine HMW-Kininogen. Fed. Proc. 36:1064, 1977.